With the improvement in a network transmission speed and the increase in a network capacity, optical signals are increasingly used for short-distance communication and medium-distance communication. As a light source for an optical signal, a compact low-power light-emitting element capable of performing direct modulation is employed. Examples of a light-emitting element include a Laser Diode (LD) such as a Vertical Cavity Surface Emitting Laser (VCSEL). In order to drive a light-emitting element, a driving circuit is used for performing differential amplification on a driving signal for a light-emitting element and driving the light-emitting element with the amplified signal (see, for example, “120-Gb/s VCSEL-Based Parallel-Optical Interconnect and Custom 120-Gb/s Testing Station”, JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 22, NO. 9, September 2004).